20 / 64
ENVIRONMENT REPORT
2015
page 20
Just over 38,000 tonnes of water-based cuttings and around 9,000 tonnes of treated oil-based fluid cuttings
were discharged from offshore installations on the UKCS in 2014. This is approximately 12,000 tonnes less
than was discharged in total the previous year. There was an increase, however, by nearly 4,000 tonnes of
thermally-treated oil-based fluid cuttings discharged, reducing the requirement to ship this waste to shore.
Approximately, 7,000 tonnes of oil-based cuttings were injected back into the reservoir (compared with
11,000 tonnes in 2013) consistent with the overall decline in cuttings generated, correlating to reduced
drilling activity.
Figure 10: Cuttings Discharged to Sea
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
2010
2011
2012
2013
2014
Cuttings Discharged to Sea (Tonnes)
Cuttings from Oil-Based Fluids
Cuttings from Water-Based Fluids
Source: EEMS June 2015
There is limited international data publically available on the discharge of drill cuttings, as less than half the
IOGP reporting companies provided information on oil-based cuttings in 2013. Norske Olje & Gas reported a
25 per cent increase in the generation of oil-based mud cuttings between 2012 and 2013, none of which were
reported as discharged to sea.
3.5 Atmospheric Emissions
The extraction, stabilisation and export of hydrocarbons involve several processes that give rise to atmospheric
emissions. These include combustion to provide electrical power and drive compressors and pumps; flaring of
excess gas for safety and during well testing; and incidental releases from tank loading, as well as firefighting and
refrigeration equipment.
Combustion and flaring result in emissions of carbon dioxide (CO
2
), carbon monoxide (CO), methane (CH
4
) and
oxides of nitrogen (NO
x
) and sulphur (SO
x
). Small amounts of nitrous oxide (N
2
O) are also emitted. Releases of
volatile organic compounds (VOCs) and CH
4
may occur during tank loading, while firefighting may release halons.